Method and system for monitoring a hadron beam during hadron-therapy treatment of a subject

Abstract

A method for monitoring a hadron beam during hadron-therapy treatment of a subject including tumour cells labelled with a radiopharmaceutical product, in which the hadron beam includes a plurality of discrete hadron bursts, the method including the following steps: when a burst impacts on the subject, detecting the prompt gamma generated by the interaction of the hadrons of the burst with the tissues of the subject using a Compton telescope and reconstructing an image of the interaction volume; when no burst impacts on the subject, extracting the position of the tumour cells labelled with the radiopharmaceutical product using the Compton telescope and reconstructing an image of the total volume of the tumour; comparing the image of the interaction volume and the image of the total volume of the tumour so as to locate the measured interaction volume relative to the measured total volume of the tumour.

The invention claimed is: 
     
       1. A method for monitoring a hadron beam during hadron-therapy treatment of a subject comprising tumour cells labelled with a radiopharmaceutical product having a radioisotope emitting a positron and a de-excitation gamma ray in quasi-coincidence, wherein the hadron-therapy treatment is delivered according to a treatment plan comprising predefined parameters as a function of time in order to define at least one characteristic of the hadron beam over time during the hadron-therapy treatment, wherein the hadron beam comprises a plurality of discrete bunches of hadrons having the same acceleration phase and emitted at a predefined frequency by an acceleration device, the method comprising the following steps:
 when a bunch of hadrons impacts on the subject:
 detecting the prompt gammas generated by the interaction of the hadrons of the bunch of hadrons with the tissues of the subject by means of a liquid-xenon Compton 
 
 telescope;
 using the prompt gammas detected to reconstruct an image of the interaction volume inside which the hadrons of the bunch of hadrons interact with the subject's tissues; 
 
 when no bunch of hadrons impacts on the subject:
 extracting the position of the tumour cells labelled with the radiopharmaceutical product by simultaneously detecting the de-excitation gamma ray and two annihilation gamma rays produced by the positron by means of the Compton telescope; 
 reconstructing an image of the total volume of the tumour to be treated by the hadron beam during the hadron-therapy treatment; 
 
 comparing the image of the interaction volume and the image of the total volume of the tumour so as to locate the measured interaction volume relative to the measured total volume of the tumour; 
 each time the measured interaction volume is at least partially included in the measured total volume of the tumour, computing the deviation between, on one hand, the position of the measured interaction volume in the measured total volume of the tumour and, on the other, a predefined position of the interaction volume in the total volume of the tumour defined in the treatment plan. 
 
     
     
       2. The method according to  claim 1 , wherein the image of the interaction volume is obtained for each bunch of hadrons impacting on the subject. 
     
     
       3. The method according to  claim 1 , further comprising a step wherein the deviation between the predefined position of the interaction volume and the position of the interaction volume measured relative to the measured total volume of the tumour is compared to a predefined threshold. 
     
     
       4. The method according to  claim 1 , wherein, each time the deviation is greater than the predefined threshold, the method comprises a step of computing at least one new parameter of the hadron beam so as to correct at least one characteristic of the hadron beam. 
     
     
       5. The method according to  claim 1 , wherein the subject is positioned on a motorised mechanical support configured to move the subject relative to the beam during the hadron-therapy treatment and wherein at least one of the predefined parameters of the treatment plan corresponds to the spatial position of the motorised mechanical support. 
     
     
       6. The method according to  claim 5 , wherein, each time the deviation is greater than the predefined threshold, the method comprises a step of computing the parameter of the treatment plan corresponding to a new spatial position of the motorised mechanical support so as to correct at least one characteristic of the hadron beam. 
     
     
       7. The method according to  claim 1 , wherein the new parameter of the hadron beam is sent to the acceleration device, which modifies at least one characteristic of the hadron beam so as to modify the position of the interaction volume relative to the measured total volume of the tumour. 
     
     
       8. The method according to  claim 1 , wherein, each time the deviation is greater than the predefined threshold, the method comprises stopping the hadron beam. 
     
     
       9. The method according to  claim 1 , further comprising a step of reconstructing a three-dimensional image sequence resulting from the merging of a three-dimensional image of the interaction volume with a three-dimensional image with the total tumour volume in the same Compton camera reference. 
     
     
       10. The method according to  claim 1 , wherein the Compton telescope is a liquid-xenon Compton telescope. 
     
     
       11. A system for monitoring a hadron beam during hadron-therapy treatment of a subject comprising tumour cells labelled with a radiopharmaceutical product having a radioisotope emitting a positron and a de-excitation gamma ray in quasi-coincidence, wherein the hadron-therapy treatment is delivered according to a treatment plan comprising predefined parameters as a function of time in order to define at least one characteristic of the hadron beam over time during the hadron-therapy treatment, wherein the hadron beam comprises a plurality of discrete bunches of hadrons emitted at a predefined frequency by an acceleration device, the system comprising:
 a beam imaging module configured to receive the data acquired from a liquid-xenon Compton telescope when a bunch of hadrons impacts on the subject and to analyse these data so as to determine the emission point of the prompt gammas generated by the interaction of the bunch of hadrons with the subject's tissues from which an image of the interaction volume inside which the hadrons of the bunch of hadrons interact with the tissues is reconstructed; 
 a tumour imaging module configured to receive the data acquired by the Compton telescope, when no bunch of hadrons impacts on the subject and to analyse these data so as to extract the position of the tumour cells labelled with the radiopharmaceutical product by simultaneously detecting the de-excitation gamma ray and two annihilation gamma rays produced by the positron and use the position of the tumour cells to reconstruct an image of the total volume of the tumour to be treated by the hadron beam during the hadron-therapy treatment; and 
 an evaluation module configured to compare the image of the interaction volume and the image of the total tumour volume so as to locate the measured interaction volume relative to the measured total volume of the tumour and, each time the measured interaction volume is at least partially included in the measured total volume of the tumour, to compute the deviation between, on one hand, the position of the measured interaction volume relative to the measured total volume of the tumour and, on the other, a predefined position of the interaction volume within the total volume of the tumour defined in the treatment plan. 
 
     
     
       12. The system according to  claim 11 , wherein the evaluation module is further configured to compare the deviation between the predefined position of the interaction volume and the position of the interaction volume measured relative to the measured total volume of the tumour, to a predefined threshold. 
     
     
       13. The system according to  claim 11 , further comprising a correction module configured to compute at least one new parameter of the hadron beam, each time the deviation is greater than the predefined threshold, in order to correct at least one characteristic of the hadron beam. 
     
     
       14. The system according to  claim 11 , wherein the correction module is furthermore configured to send the new parameter of the hadron beam to the acceleration device which modifies at least one characteristic of the hadron beam so as to modify the position of the interaction volume relative to the measured total volume of the tumour. 
     
     
       15. The system according to  claim 11 , further comprising a safety module configured to send the acceleration device the instruction to stop the hadron beam each time the deviation is greater than the predefined threshold.